The typical American underestimates how many Protestants there are in the U.S., and vastly overestimates the number of religious minorities such as Mormons, Muslims, and atheist/agnostics, according to a new study.

Grey Matter Research and Consulting asked 747 U.S. adults to guess what proportion of the American population belongs to each of eight major religious groups: Protestant, Catholic, Jewish, Mormon, Muslim, atheist/agnostic, believe in God or a higher power but have no particular religious preference, and any other religious group.